1. Field of the Invention
The invention relates to an optical disc such as a DVD the like, and a method of manufacturing the optical disc, particularly to a method of manufacturing an optical disc which is placed in the in-line row.
2. Related Art
An optical disc, for example, a DVD is normally constituted by bonding two pieces of disc halves, namely, a first disc half and a second disc half.
These disc halves are generally molded by an injection molding unit (injection molding machine).
An optical reflection film or protection film is formed on a substrate serving as a disc half by a sputtering technique, and finally a first disc half and a second disc half are bonded to each other to manufacture a DVD.
A technique for manufacturing a DVD by a consecutive product line, particularly by in-line has not been conventionally completed. Accordingly, a DVD manufactured conventionally does not possess sufficient uniformity of quality. Further, the manufacture of a DVD requires different steps such as an injection molding step, a Cooling step, a sputtering step, a binding step and the like, each of which are respectively different in operation. As a result, the number of steps increases indispensably. Accordingly, there occurs loss in time, and hence a DVD is not manufactured efficiently.
Further, for a DVD comprising a pair of disc halves, there is one type that stores information in one disc half and another type that stores information in both disc halves. In the latter case, in an injection molding step of the foregoing steps, a mold used in the injection molding step is provided with different stampers that are attached to the inner walls thereof for storing different information in the same mold. This is done because two disc halves storing different information therein are normally manufactured at the same time (see, e.g., Japanese Patent Paid-Open Publication No. 9-155986).
However, if these stampers are assembled in the same mold, it is difficult to discriminate them from each other, and hence confusion results. Further, when the disc halves serving as molded products are taken out from the mold using a production take-out unit, the disc halves storing therein different information are taken out while discriminating them from each other, which leads to confusion. Still further, if the disc halves are transferred to a subsequent step, for example, a cooling step, they have to be once separated from the same mold, and are transferred by a line, leading to the increase of the number of steps. Under the circumstances, there is a problem in that a conventional bonding unit eventually results in an increased manufacturing cost.
In view of the foregoing problems, it is an object of the invention to provide a method of manufacturing an optical disc capable of manufacturing a high quality optical disc by a consecutive product line with high efficiency. It is another object of the invention to improve a productivity in an injection molding step.
Inventors of this application endeavored themselves to study the foregoing problems and completed the invention based on the finding the provision of a buffering step for stocking disc halves of an optical disc in the product line, and the molding of a pair of disc halves by different molds in an injection molding step, thereby consecutively and efficiently manufacturing an optical disc.
That is, a first aspect of the invention relates to a method of manufacturing an optical disc constituted by bonding two disc halves wherein a first disc half storing information therein and molded by a mold of a first injection molding unit and a second disc half storing information therein, which information is different from that stored in the first disc half, and molded by a mold of a second injection molding unit are paired and bonded to each other.
A second aspect of the invention relates to a method of manufacturing an optical disc constituted by bonding two disc halves comprising at least a step of molding a first disc half storing information therein by a mold of a first injection molding unit and a step of molding a second disc half storing information therein, which information is different from that stored in the first disc half, by a mold of a second injection molding unit.
A third aspect of the invention relates to a method of manufacturing an optical disc wherein the mold of the first injection molding unit and the mold of the second injection molding unit are formed of respectively a multicavity mold.
A fourth aspect of the invention relates to a method of manufacturing an optical disc wherein a plurality of stampers provided in the mold of the first injection molding unit are the same and a plurality of stampers provided in the mold of the second injection molding unit are the same.
A fifth aspect of the invention relates to a method of manufacturing an optical disc constituted by bonding two disc halves comprising an injection molding step for molding a first disc half storing information therein by a mold of a first injection molding unit and molding a second disc half storing information therein, which information is different from that stored in the first disc half, by a mold of second injection molding unit, a cooling step for cooling the disc halves after the injection molding step, a sputtering step for forming reflection films on disc halves after the cooling step, a buffering step for stocking the disc halves after the sputtering step, and a bonding step for bonding the two disc halves and integrating them after the buffering step.
A sixth aspect of the invention relates to a method of manufacturing an optical disc wherein a cooling unit used in the cooling step is disposed between first and second injection molding units used in the injection molding step.
A seventh aspect of the invention relates to a method of manufacturing an optical disc wherein the first disc half molded by the mold of the first injection molding unit and the second disc half molded by the mold of the second injection molding unit are separated from each other after the injection molding step, and transferred to the cooling step.
An eighth aspect of the invention relates to an optical disc manufactured by either of the first to seventh aspects of the invention.
It is possible to employ a construction combined at least two aspects of the invention selected from the first to seventh aspects of the invention if it meets the object of the invention.
According to the invention, an optical disc can be continuously and efficiently manufactured by a consecutive product line without always stopping the flow of a work (disc halves) by arranging the cooling step after the injection molding step, the sputtering step after the cooling step, the buffering step after the sputtering step, and the bonding step after the buffering step.
Further, it is possible to achieve efficiency of the injection molding step by pairing and bonding two disc halfs comprising the first disc half storing therein information and molded by the mold of the first injection molding unit and the second disc half storing therein information, which information is different from that stored in the first disc half, and molded by the mold of the second injection molding unit.